The handling and lifting systems generally comprise a handling structure (crane or gantry crane) which is integral with the floating building. Said structure comprises an articulated arm and is provided with a pulley which is capable of guiding a lifting cable at the free end of the articulated arm in the vertical direction and with a winch which is capable of winding/unwinding said cable.
The cable is provided with first hooking means which are capable of cooperating with second hooking means in order to suspend the vessel from the lifting cable.
The articulated arm allows the lifting cable to be positioned above the area for recovery or for launching in order to wind up or launch the vessel and above the storage area situated on the floating building in order to recover or store the vessel.
Conventionally, the first hooking means consist of a hook which is capable of cooperating with a ring that is secured on the vessel.
When the seagoing vessel is suspended from the lifting cable, it oscillates around an equilibrium position in which it is horizontal and pivots around the lifting cable.
This is all the more problematic as the floating building is subject to the swell. The seagoing vessel is therefore easily unbalanced and is likely to strike strongly against the structure of the floating building or the lifting and handling means or even the stevedores.
Furthermore, the transit movements carried out by the articulated arm via the lifting cable between the position for recovering or for launching and the storage position on the boat, even if they are slow and controlled, generate, aside from said critical excitation, supplementary spurts which further excite the movements of the vessel at the end of the crane cable. Said movements can make the recovering and launching operations difficult.
Thus, in relation to the state of the sea during the maneuver, the operation can turn out to be perilous for the equipment (risks of shocks between the vessel and the sea, the floating building or the handling structure) or for the people in charge of the operation (risk of shocks between the vessel and an operator).